Calc- prove sinh(x) and cosh(x) identities?

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Homework Help Overview

The discussion revolves around proving the identity cosh(2x) = cosh²(x) + sinh²(x), utilizing the definitions of hyperbolic sine and cosine functions.

Discussion Character

  • Exploratory, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the expansion of the squares of the hyperbolic functions and express confusion regarding the steps involved in the proof.

Discussion Status

Some participants have provided guidance on expanding the squares of the binomials, while others express their confusion about the process. There is a mix of attempts to clarify the steps involved.

Contextual Notes

Participants are working within the constraints of homework expectations, which may limit the type of assistance they can provide to one another.

J.live
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Homework Statement



Prove

cosh(2x)= cosh^2(x) + sinh^2(x)


Homework Equations




sinh(x) ≡ [ e^(x) - e^(-x) ] / 2

cosh(x) ≡ [ e^(x) + e^(-x) ] / 2


The Attempt at a Solution




= { [ e^(x) + e^(-x) ] / 2 }² + { [ e^(x) - e^(-x) ] / 2 }²

= [ e^(x) + e^(-x) ]² / 2² + [ e^(x) - e^(-x) ]² / 2²

... gets confusing after this. Thanks in advance.
 
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J.live said:

Homework Statement



Prove

cosh(2x)= cosh^2(x) + sinh^2(x)


Homework Equations




sinh(x) ≡ [ e^(x) - e^(-x) ] / 2

cosh(x) ≡ [ e^(x) + e^(-x) ] / 2


The Attempt at a Solution




= { [ e^(x) + e^(-x) ] / 2 }² + { [ e^(x) - e^(-x) ] / 2 }²

= [ e^(x) + e^(-x) ]² / 2² + [ e^(x) - e^(-x) ]² / 2²

... gets confusing after this. Thanks in advance.

How is it confusing? All you are doing is expanding the squares of two binomials. You know how to expand (a + b)2, right?
 
Have you tried expanding the brackets on the numerators?
 
J.live said:
confusing

Not the right attitude ! :)
 

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